1. Field of the Invention
This invention relates to the field of data transmission systems, and particularly data transmission systems employing networking equipment for transmission of digital information in the form of facsimile transmission to various communications equipment.
2. Description of the Prior Art
Facsimile (fax) devices are a popular mechanism for transmission of information. The recent advancement of technology has led to the development of many types of fax devices.
One of the distinguishing factors among the different types of fax devices is the minimum scan line time requirement of each type of device. The minimum scan line time is defined as the minimum amount of time required between the end of reception of a faxed line of information and the reception of the next faxed line of information. In older fax machines, this minimum scan line time tended to be longer in duration, whereas in more recently-developed fax machines, the minimum scan line time is much smaller or even zero.
Even more recently-developed fax machines utilize error correction algorithms to detect and correct errors. These types of fax machines generally include memory or storage space, for example, 64 Kbytes of Random Access Memory (RAM), for storing fax information that is then processed for use by a fax user. During such processing, errors are detected and corrected in those fax machines supporting error correction mode (ECM). The inclusion of memory in fax machines allowed manufacturers of fax machines to implement ECM capability in such machines, which in turn resulted in the capability to send information using very short or zero minimum scan line times.
While manufacturers of fax machines have recently included ECM capability in their fax machines, for the most part they have failed to update the algorithms included in the fax machines which do not have ECM capability. In fact, even those machines that do have ECM capability do not include updated algorithms to account for the update in ECM capability thereby resulting in fax transmissions having a minimum scan line time exceeding that which is actually necessary.
Longer scan line times effectively increase transmission times thereby resulting in longer telephone calls with added costs to the fax user. Furthermore, longer scan line times decrease transmission line throughput thereby preventing the use of an otherwise larger number of fax machines for simultaneous transmission of information thereto.
Therefore, a method and apparatus is needed for increasing the effective transmission time for transferring fax information to one or more fax machines through a packet switching network environment.
Briefly, a preferred embodiment of the present invention includes a fax system employed in a packet switching network environment for use by users for transmission of fax information and including a network device coupled, through a network interface, to one or more communications devices for transmitting a processed fax message through the network interface to one or more of the communications devices, each of the communications devices being capable of receiving fax information and having a predetermined minimum scan line time therefor. Prior to the transmission of the processed fax message, the network interface is adapted to transfer a first frame from the communications devices to the network device, said first frame for indicating whether or not a particular communications device supports Error Correction Mode (ECM) and, if the particular communications device supports ECM, the network device for transmits fax information through the network interface to the particular communications device using approximately zero minimum scan line time, thereby decreasing costs to the users of the fax system.
These and other objects and advantages of the present invention will no doubt become apparent to those skilled in the art after having read the following detailed description of the preferred embodiment illustrated in several figures of the drawings.